Chattanooga Shale in Kentucky. 129 



unconformity at the base of the Chattanooga shale, the previ- 

 ously adduced evidence of the age of the shale will be consid- 

 ered chiefly. 



Devonian fossils have been found by various geologists 

 in the lower part of the Chattanooga shale in Kentucky 

 and in its equivalent, the new Albany shale, in Indiana. 

 For a summary of the literature relating to the Devonian 

 age of the. Ohio shale which has appeared previous to 

 1898, the reader is referred to Dr. George H. Girty's* 

 important contribution to the age of the Chattanooga shale 

 in eastern Kentucky. Somewhat later the writer f published 

 a short list of Devonian fossils obtained from the Chattanooga 

 shale on the western side of the Cincinnati geanticline. The 

 whole of the Chattanooga shale was generally considered to be 

 of Genesee age until Prof. H. S. Williams;}: reported that Car- 

 boniferous fossils appeared in the topmost beds of the formation 

 at Irvine. The excellent stratigraphic work done by Foerste 

 and Morse§ in northern Kentucky has shown that these Car- 

 boniferous fossils at Irvine occur in beds which are the south- 

 ern extensions of the Berea, Bedford, and Sunbury formations 

 of southern Ohio. They have shown that about 4 feet of the 

 uppermost beds previously included in the 150 feet of the 

 Ohio or Chattanooga shale in east central Kentucky are the 

 stratigraphic equivalents of beds which in northern Ohio imme- 

 diately follow the Ohio shale and have a total thickness of about 

 150 feet. The thinning of these beds in crossing southern 

 Ohio and northern Kentucky, though very marked, harmonizes 

 fully with the attenuation which the Ohio shale suffers in being 

 reduced from a thickness of more than 2400 feet east of Cleve- 

 land to less than 150 feet at Irvine, Kentucky. 



On the basis of diastrophism Grabau,|j Schuchert,^[ and 

 Ulrich** have referred the Chattanooga shale in Tennessee to 

 the Mississippi an. These authors, though differing widely as to 

 the direction of movement of the transgression, agree in assum- 

 ing that it culminated in the deposition of the Chattanooga 

 shale in Mississippian time. Concerning this correlation and 

 the method by which it was derived, it is perhaps sufficient 

 to quote Professor Schuchert's remarks on the diastrophic 

 method. He states : 



* Description of a Devonian fauna found in the Devonian black shale of 

 eastern Kentucky, this Journal, vol. vi, p. 385, 1898. 



f Bull. U. S. Geol. Survey, No. 244, p. 20, 1905. 



% This Journal, vol. iii, p. 398, 1897. 



§ Jour, of Geology, vol. xvii, pp. 164-167, 1909. 



I Types of Sedimentary Overlap, Bull. Geol. Soc. America, vol. xvii, pp. 

 599-701, 1906. 



^[ Paleogeography of North America, Bull. Geol. Soc America, vol. xx, 

 p. 441, 1910. 



**Eevision of the Paleozoic Systems, Bull. Geol. Soc. America, vol. xxii, 

 No. 3, p. 307, pi. 29, 1911. 



